During the last few years, many studies have shown that liposomes can be used for encapsulation and transfer of an active substance into cells. To this end, phospholipid vesicles have been mainly prepared by physical techniques such as ultra-sounds, the so called "French press" technique or chemical procedures by using organic solvents or detergents followed by elimination of the latter.
However, the liposomes obtained nowadays present either structures or dimensions which do not always permit either encapsulation of certain macromolecules of a cumbersome nature or encapsulation of a relatively high quantity of active substance, with encapsulated quantities remaining until now limited to certain values.